This invention relates to improvements in data display systems which are adapted for use with radar indicators and video storage devices therefor of the type wherein data is received at a relatively low rate and displayed at a different rate, generally many times faster, to obtain a relatively non-flickering, steady high resolution image. The invention has particular application in airborne weather radar systems and radar navigation sytems.
A basic display system and radar indicator of the above type is described in U.S. Pat. No. 3,803,600 and an improvement system is described in U.S. Pat. application Ser. No. 418,154, filed Nov. 21, 1973 now U.S. Pat. No. 3,964,064. It was explained in those documents that a radar return signal is converted into a train or trains of binary bits and the bits temporarily stored in an input buffer at a rate selected in accordance with desired radar range. The bits are optionally integrated to eliminate extraneous signals, such as those caused by noise or other interference and subsequently entered from the input buffer into a main memory where the bits are stored. It is also explained how, at the proper time for display, the memorized bits related to a particular radar return signal are recalled from the memory and stored into an output buffer from whence they are subsequently called for display twice in succession before the memorized bits corresponding to the next radar return signal to be displayed are called from the memory. This means of storage and display permits the quality of the display to be independent of the pulse repetition frequency of the radar system and hence a minimum pulse repetition frequency could optionally be used and still retain a relatively bright, continuous display. As a result, the average power consumed by the transmitter portion of the radar system could be much less than that required by systems having a higher pulse repetition frequency.
Although the above cited art showed a main memory in the form of a continuously recirculating memory since that form of memory was economically advantageous and hence used in the preferred embodiment of the invention, a random access main memory was contemplated to be within the scope of that art since a random access memory (RAM) could obviously be substituted for the recirculating memory.